Preparation of mixtures, particularly of concrete



P. AUGUST Dec. 15, 1964 Filed July 11 1962 JNVENTOR. P0810 A UGl/JT United States Patent Ofilice 3,lfii, id Patented Dec. 15, 1964 Filed July 11, 1962, er. No. 208,994 7 Claims. (Cl. 259-154) My present invention relates to certain new and useful improvements in mixers, particularly of concrete or like mixers.

Concrete mixers as hitherto proposed operate either periodically or continuously. Batch mixers are advantageous insofar as proportioning of the mixture components is effected by weight with the required accuracy. However, the output of a periodically operating machine is always less than that of a continuously operating one. A continuously operating mixer, on the other hand, is inadvantageous because proportioning of the mixture components is effected by volume and lacks of uniform accuracy.

The present invention aims at improving the preparation of mixtures, particularly of concrete, in such a manner that proportioning accuracy obtained by Weight is advantageously combined with high output.

An object of the invention is to provide an improved mixer consisting of a known continuously operating mixer and of a charging receptacle preferably constructed as a lifting tub, wherein said charging receptacle comprises pro-mixing means for distributing the dry mixture components as homogeneously as possible in the whole batch of materials proportioned by weight and introduced per batch into said receptacle, and the said mixer is provided with a charging chute and with a screw conveyor extending through the whole length of the closed bottom of said chute for taking the materials from all parts of said chute bottom portion and thereby improving the distribution of the mixture components and continuously delivering said materials to said mixer.

The said charging receptacle conveniently contains a stirring device as material distributing means.

This charging receptacle, as stated, is preferably constructed as a lifting tub. For lifting and lowering this tub the machine comprises a winch mechanism and the tub-guiding means are so arranged that for discharging the contents of the tub the same is gradually tilted as it approaches its final discharging position.

The tub-guiding means of the said lifting tub comprise a pair of guide and carrier'wheels and a pair of guide rollers in connection with said tub, and a pair of guide rails for said guide and carrier wheels and of guide grooves for said guide rollers, these grooves being formed in part by said guide rails and in part by branches of said rails, these guide rails and said guide grooves being so arranged as to cause said lifting tub to be gradually tilted as it approaches its final discharging position and to be gradually tilted back as it starts moving downwards from its discharging to its charging position. Owing to this arrangement the materials are discharged from the lifting tub into the said charging chute over the whole length of the screw conveyor in said chute.

The screw conveyor provided on the bottom of the said chute has a conveyance capacity which gradually increases from its free end towards its opposite end which abuts the rear end of a mixing screw of the said mixer. This increase of the conveyance capacity may be obtained by using a screw having a cylindrical shaft with an externally conical screw blade mounted thereon, or a screw having a cone-shaped shaft and an externally cylindrical screw blade, or a screw of increasing pitch.

A water supply pipe is arranged above the mixing trough of the screw mixer extending across the same and being provided with a magnetically operated valve which is controlled by the switch of the driving motor of the screw mixer.

In order to avoid interruptions of the continuous operation of the screw mixer, its mixing trough is advantageously provided below its discharge opening with an elastically suspended concrete-storing receptacle capable of controlling by way of suitable known switch means the operation of the driving motor of the screw mixer.

Finally, suitable switch means may be provided for automatically controlling the driving motor of the lifting tub in dependence of at least its discharging operations.

A preferred embodiment of the mixer has been schematically illustrated on the accompanying drawing and will now be described in detail with reference thereto.

FIG. 1 is a schematic side view of the mixer and FIG. 2 is a fragmentary schematic top view showing the driving means of the lifting tub which constitutes the charging receptacle of the mixer. 1

The improved concrete mixer 1 as illustrated comprises a mixing trough 2 which in operative condition of the machine is in inclined position and is provided at its upper end with a discharge opening (not shown) and at its lower end with a chute 3 the bottom of which extends coaxially with the mixing trough 2 and is conveniently provided with an opening for cleaning purposes and with a trap-door 3' for said opening.

The mixing trough 2 comprises a known screw mixer 4 and coaxially therewith the chute 3 contains in its bottom portion a screw conveyor 5. Both the mixing screw 4 and the conveying screw 5 are mounted on one and the same shaft 6 operated by means of a chain or like transmission 7 from a driving motor 8.

Whereas the charging chute of knowncontinuously operating screw mixers, for the purpose of proportioning the mixture components by volume, is subdivided by several partition walls and the mixing trough is provided with a special cement supplying and proportioning means, said partition walls and said cement proportioning device are intentionally dispensed with in accordance with the present invention.

For obtaining a uniform quality of the mixture to be prepared, the mixture components are proportioned by weight by suitable weighing means 27 associated with the lifting tub 9 in its lower charging position. This tub 9 is supported and guided on a pair of guide rails 11 by means of a pair of guide and carrier wheels 10 in combination with at least one guide roller, preferably a pair of guide rollers 12. The base 31 of the weighing means 27 is located between and is secured to the guide rails 11. The movable weighing platform 39 thereof is positioned between the guide rails ll so that the tub 9 will, in its lower charging position, rest on said movable weighing platform and permit its weight and that of its contents to be determined.

For operating i.e. for lifting and lowering the substantially cylindrical tub 9 having a discharge opening 9', a driving geared motor 13 provided with a switch 28 which advantageously is a pole changing motor is suitably mounted on top members of the machine frame and is operatively connected by means of a chain or like transmission 14 and of a shaft 14' (FIG. 2) with a rope drum 15 for winding up and off a rope or cable 18 having one end fixed at 16 on the machine frame, passing around a rope pulley 17 of the lifting tub 9 and being fastened at its other end on the drum 15, the arrangement being such that by winding up and off the rope or cable 18 the tub 9 is caused to move in upward, respectively downward direction along the guide rails 11.

The-lifting tub 9 is conveniently provided with a rotary stirring device 32 capable of being operated by the carrier wheels It? in their rolling contact with the guide rails, said wheels being fixedly mounted on the shaft of said stirring device.

In accordance with an important feature of the invention, the guide rails 11 are composed each of a first mainrail portion 11a extending in inclined direction from the ground level into the open upper part of the chute 3 of the screw mixer in its operative position, of a second rail portion 11b extending in a direction substantially parallel to the bottom of the chute 3, and of a third rail portion 110 extending downwardly in an inclined direction with regard to said second rail portion 11b. The guide rails 11 of U- shaped cross section further form each a guide groove for the guide rollers 12. Near the upper end of each rail portion 11a the guide groove forms a branch 19 composed of a first downwardly inclined branch portion 19a, of a second branch portion 19b substantially parallel to the bottom of the chute 3, and of a third branch portion 190 projecting downwards in a direction substantially perpendicular to said second branch portion 19b.

The arrangement of the guide rails 11 and of the guide grooves 19. for the guide and carrier wheels 10, respectively for the guide rollers 12, is such that when the guide rollers 12 of the upwardly moving tub 9 reach the branches 19 and move along the latter, while the guide and carrier wheels 10 move along the rail portions 11a, 11b, 110, the lifting tub is caused to rotate around its axis and its outlet 9' is tilted in such a maner that the discharge of the tub contents takes place gradually over the whole length of the chute 3 and of the screw conveyor provided in the latter.

The screw conveyor 5 according to another feature of the invention has a conveyance capacity which gradually increases from its free end towards its opposite end which abuts the rear end of the mixing screw 4. For this purpose the screw blade may be externally cone-shaped on a cylindrical shaft. Alternatively this shaft may be coneshaped and the screw blade externally cylindrical. Finally the arrangement may also be such that the screw has a gradually increasing pitch.

This feature of the invention in co-operation with that of the gradual discharge of the tub contents over the whole length of the screwconveyor 5 improves the homogeneous distribution of the mixture components performed in the lifting tub 9 by the pre-mixing means contained therein, with the advantageous result that the materials are de livered by said screw conveyor from all parts of the bottom portion of the chute 3 to the mixing screw 4 not only in very homogeneous condition, but also in a continuous manner independently of the periodical charging per batches of the lifting tub 9 and by the latter to the chute 3.

The mixing operation performed by the screw mixer may thus proceed in a continuous manner provided the successive batches of dry mixture components are delivered by the lifting tub 9 to the chute 3 in such quantities that said mixture components are always available in said chute.

In the case of the preparation of a mixture, such as concrete, with a liquid component, such as water, the mixing trough 2 is provided with a water supply pipe 20 extending transversely to the axis of said trough and being provided in a known manner along its upper wall portion with one or more rows of outlet openings and with a dome-shaped baflle plate 21 capable of distributing the water supplied by the pipe 20 over the whole Width of the mixing trough 2 with the additional advantage that when the delivery of water to the pipe 20 is interrupted the water supply to the mixing trough is stopped instantaneously.

In order to ensure the continuous operation of the mixer and a correspondingly high output of the machine, it is necessary to continuously withdraw the concrete prepared and discharged by the screw mixer. This, however, is rather difficult if pails or carts are to be used. Therefore, a concrete-collecting and storing receptacle 24 is conveniently provided below the discharge opening of the mixing trough 2. This receptacle is suitably suspended at least at one side by means of a spring indicated at 23 and capable of resisting the weight of the nearly filled receptacle 24 and of yielding when the latter is entirely filled. The movement of this receptacle which thus occurs as soon as the same is entirely filled is used for operating a switch indicated at 22 for controlling the motor 8 and, if desired, at the same time a magnetically operated valve 29 for the water pipe 20.

The screw mixer 1 is advantageously mounted in a known manner on a pair of carrier wheels 25. A drawbar 26 serves for connecting the machine to a tractor.

The operation of the mixer is as follows:

In its lower position the lifting tub 9 is batchwise charged with the dry mixture components which are proportioned by weight so that the mixture will always be of the desired quality in as far as the proportions of the components are concerned. The proportioning and charging operations as such do not form part of this invention and are performed in any suitable known manner.

As soon as the tub is charged, the motors 8 and 13 are started. The rope drum 15 is operated by the motor 13 and causes the tub 9 to move upwards on the rails 11. As soon as the guide rollers 12 enter the branch portions 1901, the tub 9 starts rotating and discharging its contents. As the carrier wheels 10 of the tub 9 continue advancing from the rail portions 11a on the rails portions 11b and 11c, while the guide rollers follow the guide grooves in the branch. portions 19a, 19b, 19c, the discharge of the rotating tub 9 gradually proceeds over the whole length of the chute 3 and of the screw conveyor 5 which operated by the driving motor 8 takes the materials from all parts of the length of the bottom portion of the chute 3 and continuously delivers the same to the mixing screw 4. in the mixing trough 2 thereby improving the homogeneous distribution of the mixture components and continuously feeding the screw mixer 2, 4 which thus is enabled to continuously prepare the concrete and discharge it into the storing receptacle 24, which at its lower end is provided with a trap-door or the like. As long as the receptacle 24 is continuously emptied, operation of the mixer proceeds without interruption. When, however, the storing receptacle becomes entirely filled and its weight becomes higher than the resistance of the spring or springs by means of which the receptacle is elastically suspended, then the switch 22 automatically disconnects the driving motor 8, stops the rotation of the shaft 6 of the mixing screw 4 and interrupts the water supply to the pipe 20 by means of the afore-mentioned magnetically operated valve, as soon as thereafer the storing receptacle 24 is in part or entirely emptied, then its slight upward. movement caused by said springs will produce the re-connection of the driving motor and thus cause the mixer to continue operating.

The driving motor 13 conveniently is a pole changing motor and its operation may be automatically controlled by suitable known switch means in dependence of at least the discharging operations of the lifting tub 9.

What I claim is:

1. A mixer, particularly a concrete mixer, comprising weighing means for proportioning the mixture components associated with a charging receptacle for batchwise receiving the mixture components, this receptacle being constituted by the tub of a tub lift and being provided with a rotary stirring device, a winch mechanism including a driving motor connected with said tub for moving the same from its charging to its discharging position and vice-versa, U-shaped guide rails forming part of said tub lift, a pair of guide and carrier wheels provided on said tub and supported by upper guide surfaces of said rails, a pair of guide rollers provided on said tub and arranged in guide grooves which are formed in part by said U-shaped guide rails and in part by U-shaped branches of said guide rails, a chute having a closed bottom and a screw conveyor arranged on the bottom of said chute, and a screw mixer operatively connected with a driving motor and coaxially connected with said screw conveyor, said chute being arranged below said tub in its upper discharging position, said guide rails and said guide groove-forming branches including rail portions, respectively branch portions, extending through the open upper part of said chute and in a direction substantially parallel to the bottom of said chute, and switch means connected with the two cited driving motors for controlling their operation.

2. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein each of the said guide rails is composed of a first inclined rail portion extending from the ground level into the open upper part of the said chute, of a second rail portion extending in a direction substantially parallel to the bottom of said chute, and of a third rail portion extending downwardly in an inclined direction with regard to said second rail portion, and each of the said guide groove-forming branches is composed of a first branch portion extending from said first rail portion in downwardly inclined direction, of a second branch portion extending in a direction substantially parallel to the bottom of said chute, and of a third branch portion extending downwards in a direction perpendicular to said second branch portion.

3. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein the said screw conveyor has a conveyance capacity gradually increasing from its free end to its opposite end which abuts the rear end of the mixing screw of the said screw mixer.

4. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein the said screw conveyor comprises a cylindrical shaft and an externally cone-shaped screw blade.

5. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein one of the two switches, which is connected with the said driving motor of the said screw mixer, is arranged for its automatic operation by a known concrete-storing receptacle elastically suspended below the discharge opening of the said screw mixer.

6. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein one of the said two switches, which is connected with the said driving motor of the said screw mixer, is further connected with a magnetically operated valve provided in the water supply pipe for said screw mixer, said pipe extending in transverse direction over the mixing trough of said screw mixer.

7. A mixer, particularly a concrete mixer, as claimed in claim 1, wherein the said driving motor of the said tube lift is a pole changing motor and the said switch connected with said motor is arranged at reach of the tub of said tub lift in its discharging position.

References Cited by the Examiner UNITED STATES PATENTS 900,227 10/08 Svenson 259- X 1,304,619 5/19 Stamp 259-149 1,733,410 10/29 Johnson 259-149 1,855,420 4/32 Robb 214-2 2,608,395 8/52 August 259-161 2,756,975 7/56 August 259-161 2,948,519 8/60 Bradshaw et al 259-154 2,976,025 3/61 Pro 259-154 FOREIGN PATENTS 159,349 3/33 Switzerland.

625,250 8/ 61 Canada.

877,405 9/61 Great Britain.

1,092,437 11/54 France.

WALTER A. SCHEEL, Primary Examiner. 

1. A MIXER, PARTICULARLY A CONCRETE MIXER, COMPRISING WEIGHING MEANS FOR PROPORTIONING THE MIXTURE COMPONENTS ASSOCIATED WITH A CHARGING RECEPTACLE FOR BATCHWISE RECEIVING THE MIXTURE COMPONENTS, THIS RECEPTACLE BEING CONSTITUTED BY THE TUB OF A TUB LIFT AND BEING PROVIDED WITH A ROTARY STIRRING DEVICE, A WINCH MECHANISM INCLUDING A DRIVING MOTOR CONNECTED WITH SAID TUB FOR MOVING THE SAME FROM ITS CHARGING TO ITS DISCHARGING POSITION AND VICE-VERSA, U-SHAPED GUIDE RAILS FORMING PART OF SAID TUB LIFT, A PAIR OF GUIDE AND CARRIER WHEELS PROVIDED ON SAID TUB AND SUPPORTED BY UPPER GUIDE SURFACES OF SAID RAILS, A PAIR OF GUIDE ROLLERS PROVIDED ON SAID TUB AND ARRANGED IN GUIDE GROOVES WHICH ARE FORMED IN PART BY SAID U-SHAPED GUIDE RAILS AND IN PART BY U-SHAPED BRANCHES OF SAID GUIDE RAILS, A CHUTE HAVING A CLOSED BOTTOM AND A SCREW CONVEYOR ARRANGED ON THE BOTTOM OF SAID CHUTE, AND A SCREW MIXER OPERATIVELY CONNECTED WITH A DRIVING MOTOR AND COAXIALLY CONNECTED WITH SAID SCREW CONVEYOR, SAID CHUTE BEING ARRANGED BELOW SAID TUB IN ITS UPPER DISCHARGING POSITION, SAID GUIDE RAILS AND SAID GUIDE GROOVE-FORMING BRANCHES INCLUDING RAIL PORTIONS, RESPECTIVELY BRANCH PORTIONS, EXTENDING THROUGH THE OPEN UPPER PART OF SAID CHUTE AND IN DIRECTION SUBSTANTIALLY PARALLEL TO THE BOTTOM OF SAID CHUTE, AND SWITCH MEANS CONNECTED WITH THE TWO CITED DRIVING MOTORS FOR CONTROLLING THEIR OPERATION. 